Previous studies have shown that lung macrophages are particularly susceptible to HIV infection. The mechanism is not known. It is therefore surprising that in subjects with stable infection the HIV burden in lung macrophages is low. This proposal will test the hypothesis that the suppression of viral burden in the lung is due to the influence of the epithelium and resident cytotoxic lymphocytes that create a microenvironment inhibitory to viral uptake and replication. The hypothesis will be tested by performing the following aims: Aim 1: To determine how interactions between proteoglycans, glycosaminoglycans (GAGs) and the beta-chemokine, RANTES, affect HIV infection in alveolar macrophages. Aim 2: To determine if lung epithelium directly regulates HIV replication in alveolar macrophages; and Aim 3: To characterize the ability of autologous lung CD8 lymphocytes to modulate alveolar macrophage HIV infectivity. The ability of beta-chemokines to inhibit viral replication in monocytes is much less than for CD4+ lymphocytes, but chemokine inhibition has not been studied for the pulmonary macrophage. Initial experiments will therefore determine the extent to which recombinant RANTES influences viral uptake and replication, and how GAGs influence this interaction. Viral uptake will be determined using quantitative real time PCR (TaqMan) and viral protein production (p24). Subsequent studies will evaluate the effects of epithelial cell supernatants, co-cultures, and reconstituted pulmonary lavage fluid on viral uptake and replication in pulmonary macrophages exposed to viral isolates. Preliminary data suggest that chemokines, prostaglandins and perhaps GAGS are candidates for potential antiviral effects from the epithelial lining. Finally, we will investigate how lung epithelial fluid and epithelial cells influence the cytotoxic and non-cytotoxic activities of CD8 cells on infected macrophages. These studies should provide important insights into how changes in the lung microenvironment can influence disease progression. They may alter future designs for new therapeutic and antiviral treatments.